1. Field of the Invention
The present invention relates to electrical connectors, and, in particular, to plugs designed to reduce crosstalk between adjacent transmission paths.
2. Description of the Related Art
One type of plug used to terminate cordage (i.e., multi-wire cabling) is the 110-type patch plug, manufactured by Lucent Technologies, Inc., of Murray Hill, N.J. One end of the 110-type patch plug permanently terminates a multi-wire cable, while the other end mates removably to the insulation displacement contacts (IDCs) of a 110-type connecting block, which is also manufactured by Lucent Technologies. 110-type patch plugs are often used in voice and data transmission applications. In such transmissions, a balanced signal transmission path is formed by each pair of conductors, called the TIP conductor and the RING conductor. A typical 8-wire cable can therefore support four different voice or data signal transmission paths.
A 110-type patch plug has one or more pairs of contacts (typically 1, 2, 3, or 4 pairs) that form the electrical connections between the conductors of a multi-wire cable and the IDCs of a 110-type connecting block. One end (i.e., the mating end) of each patch-plug contact is a blade that engages a split-beam contact of the 110-type connecting block. The other end (i.e., the cable end) of each patch-plug contact has a split-beam contact (e.g., an IDC) that terminates one of the cable conductors. The blades are sequenced in a linear alternating fashion between TIP and RING conductors in order to be aligned with the split-beam contacts of a 110-type connecting block.
FIG. 1 shows an exploded view of a prior-art 110-type patch plug 100. 110-type patch plug 100 of FIG. 1 has a bottom cover 102, a top cover 104, and four pairs of contacts 106, with each TIP-RING pair (T.sub.i, R.sub.i) corresponding to a single balanced transmission path. When housed within bottom cover 102, each contact 106 provides, at one end, a blade for mating with a split-beam contact of a 110-type connecting block and, at the other end, an insulation displacing contact (IDC) 110 for terminating a wire of a multi-wire cable. Depending on the particular embodiment, one or more TIP-RING pairs of contacts 106 may be designed to cross over one another, as shown in FIG. 1.
As shown in FIG. 1, contacts 106 are designed such that the open ends of IDCs 110, which receive the individual cable wires, face top cover 104. Top cover 104 has structural components that force the cable wires into the corresponding IDCs 110, thus ensuring good electrical contact between the cable wires and contacts 106 of patch plug 100 when top cover 104 is assembled onto bottom cover 102.
One common type of conventional multi-wire cabling used for telecommunications applications has one or more twisted pairs of copper wires, where each twisted pair carries the TIP and RING signals for one balanced transmission path. In order to reduce crosstalk between these transmission paths, a different twist rate is used for each different twisted pair within such cordage. A twist rate may be characterized in terms of the number of times the wires of a twisted pair circle one another over a particular length of cordage, e.g., in terms of revolutions per foot.
Near-end crosstalk refers to unwanted signals induced in one transmission path due to signals that are transmitted over one or more other transmission paths appearing at the end nearest to where the transmitted signals are injected. Near-end crosstalk often occurs when the wires, contacts, and/or other conductors that form the various transmission paths are in close proximity to one another. The twist rates for cordage for telecommunications applications is typically carefully selected and strictly maintained within the cordage to limit such near-end crosstalk.
As shown in FIG. 1, prior-art patch plugs have a volume 112 within which the twisted pairs and ultimately the individual wires are distributed from a multi-wire cable to the IDCs 110 of an 110-type patch plug. Lack of control over twist rates within volume 112 may lead to near-end crosstalk. Moreover, lack of control over routing paths within volume 112 may result in the levels of such crosstalk varying significantly from one patch plug/cordage assembly to another, due to variations in those routing paths from assembly to assembly. The resulting electrical/transmission performance variability may be intolerable for certain high-performance, high-speed telecommunications systems.